The Atlantis Massif is a prominent undersea

massif In geology, a massif ( or ) is a section of a planet's crust that is demarcated by faults or flexures. In the movement of the crust, a massif tends to retain its internal structure while being displaced as a whole. The term also refers to a ...

in the

North Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the "Old World" of Africa, Europe an ...

. It is a dome-shaped region approximately across and rising about from the sea floor. It is located at approximately 30°8′N latitude 42°8′W longitude; just east of the intersection of the

Mid-Atlantic Ridge The Mid-Atlantic Ridge is a mid-ocean ridge (a divergent or constructive plate boundary) located along the floor of the Atlantic Ocean, and part of the longest mountain range in the world. In the North Atlantic, the ridge separates the North A ...

with the Atlantis

Transform Fault A transform fault or transform boundary, is a fault along a plate boundary where the motion is predominantly horizontal. It ends abruptly where it connects to another plate boundary, either another transform, a spreading ridge, or a subduct ...

. The highest point of the massif is around beneath the surface.

Description

It is believed that the massif was formed underneath the nearby Mid-Atlantic Ridge, but pulled from underneath the ridge during the movement of the plates, about 1.5 to 2 million years ago. Geologic studies of the massif have indicated that it is not composed of the black

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...

typical of the ocean floor, but rather of dense green

peridotite Peridotite ( ) is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium (Mg2+), reflecting the high pr ...

usually found in the

mantle A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that. Mantle may refer to: *Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear **Mantle (vesture), an Eastern Orthodox ve ...

. The central dome is corrugated and striated in a way that is representative of an exposed

ultramafic Ultramafic rocks (also referred to as ultrabasic rocks, although the terms are not wholly equivalent) are igneous and meta-igneous rocks with a very low silica content (less than 45%), generally >18% MgO, high FeO, low potassium, and are composed ...

oceanic core complex An oceanic core complex, or megamullion, is a seabed geologic feature that forms a long ridge perpendicular to a mid-ocean ridge. It contains smooth domes that are lined with transverse ridges like a corrugated roof. They can vary in size from 10 ...

. An expedition to the area in 1996 made an important advance in the study of the ocean floor. It found that a steeply sloping

detachment fault A detachment fault is a gently dipping normal fault associated with large-scale extensional tectonics. Detachment faults often have very large displacements (tens of km) and juxtapose unmetamorphosed hanging walls against medium to high-grade me ...

is associated with the oceanic core complex structure. The dome was caused by mantle material being extruded to the surface. Another expedition discovered the Lost City hydrothermal field near the summit of the ridge in 2000. Another expedition in 2016, the IODP 357 expedition, targeted this massif, drilling cores.

External links

View of the Massif

Harvard University: Geology of the Atlantis Massif

References

{{Reflist Geology of the Atlantic Ocean Plate tectonics Mid-Atlantic Ridge Guyots